A new magnetite reference material, named CAGS-MAG, was prepared by the Institute of Geology, Chinese Academy of Geological Sciences. One-way analysis of variance was used to test the homogeneity of CAGS-MAG, and trend analysis was used to test the stability of CAGS-MAG during 30 months (five times). CAGS-MAG showed sufficient homogeneity and stability for use as a Fe isotope reference material. The property value was determined by an interlaboratory comparison of results from five participating laboratories, which were Institute of Geology, Chinese Academy of Geological Sciences, University of Science and Technology of China, China University of Geosciences (Beijing), Tianjin University, and Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The property value was calculated from the unweighted means of the results submitted by the participating laboratories. Uncertainties were associated with batch characterization (u_char), possibility between-bottle variations (u_bb'), and those derived from effects related to long-term storage (u_lts). The property values[δ⁵⁶Fe_IRMM-014(‰) and δ⁵⁷Fe_IRMM-014(‰)] for CAGS-MAG are 0.68 and 0.99, with a combined expanded uncertainty (k=2) of 0.10 and 0.13 respectively. CAGS-MAG can be used to validate chromatographic separation and total measurement procedures and to conduct inter-laboratory comparisons when Fe isotopes of iron ore samples, such as hematite samples and magnetite samples, were measured.